1. Field of the Invention
The present invention relates to automotive head lamps.
2. Background Art
Automotive head lamps have often employed a light bulb, a reflector, and a lens. The light bulb is typically oriented between the reflector and the lens to emit light omnidirectionally from the bulb. The light radiates from the bulb and out of the lens. The light also radiates from the bulb and reflects from the reflector out of the lens. By employing parabolic reflectors, the light from the light bulb may reflect from the reflector in a focused pattern such that the omnidirectional light is focused to radiate from the lens in a uniform manner. Thus, the light is targeted upon the desired region.
In order to prevent the omnidirectional light from the bulb from interfering with the vision of oncoming travelers, the prior art has employed louvres within head lamps. Such louvres include an array of parallel slats provided directly between the bulb and the lens such that light from the forward portion of the bulb is only permitted to exit the lens in a direction consistent with the focused light pattern from the reflector and louvres.
As automotive head lamps have continued to evolve, louvres have been subsequently replaced by bulb shields. Bulb shields are typically oriented in front of the light bulb so that light from a forward region of the light bulb is prevented from exiting the lens. Thus, the only light exiting a head lamp with a bulb shield is light from the light bulb that reflects off the parabolic reflector and therefore is focused to illuminate the required region. The bulb shield provides an alternative solution to the louvres, which is less complicated and provides desired illumination characteristics.
Louvres and bulb shields are typically associated with low beam or daytime head lamps wherein the vision of oncoming traffic is a concern. High beams are typically employed without a louvre or a bulb shield permitting omnidirectional and focused light to exit the lens. Adjustable louvres have been utilized also for adjusting the direction of illumination in head lamps that were employed by both a low beam and a high beam.
As head lamp technology has evolved, head lamp lenses have gone from glass to a transparent polymer, which provides adequate structural characteristics, adequate visual and illumination characteristics, and improvements in manufacturing and design capabilities.